When I was at school I had to take an exam on this (immense!) Graham Greene novel. It influenced our whole class profoundly. We found it very thought provoking, and held endless discussions about it - especially as we had to do quite a few analyses of the history and text involved for our exam. No wonder it is such popular exam material for the British Council, taught to many foreign students abroad (not to mention it portrays the British in a very favourable light).
As a result, the film feels a bit strange, as it is rather different in mood and style to the book (but then most films are). The strangest thing about the film is that the main character is much younger in the book than in the film (because in the film he is played- superbly- by Michael Caine). This film is quite engaging, though, and most of the book's original ideas seep through and permeate the movie. I would still suggest one reads the book first, if one can be bothered, so that one can form their own visual images of the ideas in the text in their own head first. After that, one could watch this film, which is quite beautiful, especially its location shots. The acting is superb too; one gets to finally see Brendan Fraser in a role deserving of his talent. The only other time I have seen him star in a good role was "Gods and Monsters" (with that other holy monster of the British actor elite, Ian McKellen). That one also is a film well worth watching, whether you are a Fraser fan or not. The problem with Fraser is that, due to his good looks, he's often been type-cast in stupid teenage and action movies, that were a blatant waste of his talents (a predicament that female actresses mostly have to endure, but which rarely happens to male actors).
Although the film does not fully deal with most of the historical and political ideas of the book, one gets a very clear vision of what the original story had been, most notably with that so pertinent phrase against indifference and neutrality in the face of major events in history: "Sooner or later one has to take sides, if one is to remain human". I can no longer remember if this phrase was in the G. Greene book in its exact form, but it suits the film very well, and if the scriptwriter wrote this, well done! Another nice touch of the film is the ending, where you get clippings of newspapers showing you what happened next in Vietnam, after the time this story takes place. This adds an insight to the events, which the book could not of course have given. And it is a very nice touch when at the end, Michael Caine apologises to his mistress for what he has done to Pyle and she says to him "You do not need to apologise to me" (she, of course, doesn't know of the betrayal). I do remember that at the end of the book the hero expresses the need that he could have someone to whom he could say he was sorry. In the film he has, in a way. This is a key idea in the book, and the only way to bring it forward in a visual medium such as a film is to do it in the way it was done here.
A visually scrumptious, romantic and thought provoking film. You could do worse with an evening's entertainment!